Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF TEIE INVE:NTION
.
1. Field of the Invention
This invention relates to a process for the
simultaneous catalytic hydrolysis and hydrogenation of
cyclic acetals. More specifically, this invention relates
to a process for the simultaneous catalytic hydrolysis and
hydrogenation of cyclic acstals carried out at a pH of at
least 4Ø
2. Prior Art
The preparation of diols from cyclic acetals is
known. However, the methods used have experienced unsatis-
factory catalyst life, especially where the hydrogenation
catalyst is not a no~le metal and where the hydrolysis
and hydrogenation are conducted simultaneously. U.S. .
Patent 2,8B8l492 discloses the simultaneous hydrolysis
and hydrogenation o certain hydroxy aldehydes in the
pxesence of an aqueous acidic medium and a hydrogenation
catalyst. However, in such cases when a base metal hydro-
genation catalyst i5 used the catalyst life is unsatisfactor-
ily low. U.S. Patent 2~618,663 discloses the simultaneous
hydrolysis and reduction o polyether alkano.l acetals to the
corresponding polye.ther alcohols by carrying out said
simultaneous hydrolysis and reduction in an aqueous solu-
tion conta:ining catalytic quant.ities o hydrolyzable metal
salts of mineral and organic acids with Raney nickel cata-
.
lyst and hydrogen at a pH of 4.5 to S.S to minimize corrosion
of the equipment. :U.S. Patent 3,886,21g discloses a process
for the preparation of saturated aliphatic al~ohols by the
hydrogenation of saturated or unsaturated aldehydes and/or
ketones in the presence of catalysts supported on silica
-- 2
..
gel having a surface pH o~ 6 to 10. U.S. Patent 3,492,314
discloses the hydrogenation of succinic anhydrida in the
presence of a reduced nickel-rhenium catalyst to improve
the catalyst life. However, there is still a need to further
improve the performance of catalysts in hydrogenation/
hydrolysis reactions.
SUMMARY OF THE INVENTION
Now it has been found that the catalyst life in
hydrolysis and hydroganation reactions of cyclic acetals to
1,4~butanediol is extanded by conducting said reactions at
a pH of at least 4Ø
In accordance with the invention, a process has
been found for the simultaneous catalytic hydrolysis and
hydrogenation of a cyclic acetal of the general ormula
4 ~ O
- C-M~ and mixtures thereof
/~ ~ - O~
R6 l
R3 .
wherein M is an alkyl group of 1 ko 20 carbon atoms, X is
C~O or CH~OH and Rl, R2, R3~ R4~ R5 and R6 m y
or different hydroge~ or alkyl groups of 1 to 20 carbon
atoms which comprises hydroly2ing and hydrogenating said
cyclic acetal in the presance of both an aqueous acid solu-
tion and a base metal hydrogenation catalyst at a pH of 4.0
~or more until a product o 1/4-butanediol is produced with
byproduc~ diols. :
Some spacific exampIes of cyclic acetals which
may be hydrolyzed and hydrogenated in accordance wi~h ~his
~n invention include
~'~
3 - ~
~ .. . . . . . . .. .. .
(cl-c~o)
~ CH ( C -C 2 0 ) CHO
C ~ CH-CH2-CH2--CHO ~`'
O
H3C { \CH-CH2-CEI2-CHO
~3
\ CH-CH2 -CH ~-CHO
~CH3) 2 {~c~c~2-cH2-cHO
CHO
Co/
__o\ C~HO
E~3C~ ~CH-CH-CH3
CH3
~ \Cti-C3-C!13
CHO
t~H3 ) ;~ {0~CH~ C~3
~: ~
and the corresponding alcohol (where -CHO i~ replaced with
. .
~ OEI). ~ ",
In the proce~ of this inventloxl, ~ny catalytic
amount of any o~ he metal or metal compound catalysts o~ :
the type well known and customa~ ly re:f erred to in the art
as ba~e me tal hydrogenation cataly~ts can be u~ed, The
base metQl hydrogerlatlon cataly:t may be a me1ial, ~ mix~
ture of metals or a compound of a metal wherein the metals ( 8
ox~dizes rapidly and the hydrox~de o~ t}le metal ~s~ 13 ~ol-
uble in water. Representatiue example~ o~ ~uch ba~e mei;al
hydrogenation catalys~s include nlckel, conventional Raney
n~ ckelg conventiona:L Raney nickel promo~ed with molybdenum,
conventional Raney nickel promotet3 with chromium~ granula~
foramlnou~ nic~el, granular ~or~aminou~ nickel ~ctiv~ted
with molybdenum~ chromium, cob~lt or chromium an~ molybdenum,
What i~ meant by conYentional R~ney n~ ckel i~ an
alloy of nickel and alumlnum ~rherein the aluminum is 50 to
70% by weight and wherein es~entially all of the aluminum
that can be removed by normal mean~ i8 removed,
What i~ meant by granular foraminous nickel ~ ~ a
~ree-~anding granula~ alloy o:~ the RaE~ey nickel type wlth
50 to 70~ ~y weight aluminum which has from 10 to 50~b o~
the aluminum removed from l;he alloy,
What i~ meant by convention~l Raney nickel act-
vated wi th either molyb~enum or chromLum i9 ~n alloy o:f
nickel, a~.uminum and chromium or moly~denum whereln 1 to loq6
by weight ~ 9 chromium or molybd~num, 50 to 70% by weight : :
i~ aluminum and 49 to 20% by weight i8 nickeï and whereln
e~entlall~ al'l o~ the aluminum that c~n be removed by nor-
mal mean~ i~ rernoved.
What, is meant by granular :f ~raminouB nickel
5- :
... ..
.
f~
acti~ated with.either molybden~m or chromium is a
free-standing alloy of the Raney nickel type with 50
to 70% by weight aluminum, 4~ to 20% by ~eight nickel
and 1 to 10% chromium or molybdenum which has from 10
to 50% of the aluminum removed from the alloy.
The aluminum is generally removed from the
alloy with an aquec,us alkali-metal hydroxide solution
unti`l the ~es~red amount of 31uminum is leached ~rom
the alloy. The alkali metal hydraxide solution will
generally contain a~out Q.l to 5% by weight of alkali
metal hydroxide. When more than about 50% of the aluminum
is removed, the mechani.cal strength of the nickel-
aluminum catalyst particles is reduced such that they
are no longer suitable for use in a f;xed ~ed. Representa-
tive examples of metal compounds within the scope of this
i.nvention include copper chromite~ The preferred base
~ metal hydrogenation catalysts are selected from the
~ group consisting of nickel, granular foraminous nickel,
conventional Raney nickelj conventional Raney nickel
promoted with either chromium or molybdenum and granular
foraminous nickel promoted with.either chromium or
molybdenum. Most preferred are granular :Eorami.nous
nickel, conventional Raney nickel, granular foraminous
nickel promoted with molybdenum or chromium and conven-
tional Raney nickel promoted with molyhdenum or chromium.
Th.e chromium nickel and molybdenum nickel
mixtures or alloys are available commercially from ` ~
Davison Chemical, a division of W. R Grace and Co~pany. ~ -
Chromium promoted nickel and moly~denum promoted nickel
are the most active of the hydrogenation catalysts men-
tioned herein.
In the process of th.e present in~ention, it was
~ ~,
- 6 - .
5~
~ .~
found that in the stream being hydrogenated a more active
catalyst wi.ll increase the conversion of the cyclic acetal
to 1,4-butanediol. It was ~ound that catalysts which are
less active do not promote sufficiently high conversion and
result in the prepara~ion of more undesirable byproducts.
The chromium promoted nickel and more especially the
molybdenum-promoted ni.ckel result in rapid hydrogenation and
low undeslrable byproducts. In the hydrogenation/hydrolysis
reaction of this invention, i-t is essential in order to
attain low undesirable byproducts that the hydrogenation
be conducted as fast a.~ possible to avoid competing reactions
of the aldehyde formed by hydroly~is. The presence of said
aldehydes will promote the formation of undesirable by-
products. For example, molybdenum nickel catalyst in the
process of the present invention results in less undesir-
able byproducts than Raney nickel because of its superior
hydrogenation activity.
The following equations describe the formation
believed to contribute to undesirable byproducts that are
~0 minimized with active hydrogenation catalysts:
... .
r ,c C~ C c~ 2--~ { + ~C-C-C-C~
O OH
A . B
1N2 li2~l
{ C_C_C_C~ 2~ ~ ~ HO-C-C C_C=O
/ ~ OH
C ' . . .
~IH2 ,
- OH
_ ~ ~ Ho-C~C-C-C-OH
OH
The aldehyde group~ in A, B and C undexgo reactions
producing undesirable byproducts unless these aldehyde
groups aré hydrogenated rapidly to alcohol yroups.
Hydrogenation reactions generally do not require
any high degree of hydrogenation to prevent undesirable
byproduct formation.
The base metal hydxogenation catalyst may be em-
ployed in a fin~ly divided form or slurry without a support
and dispersed in and throughout the reaction mixture, or it
may be employed in a granu1ar ~orm with aluminum as a
support or in a more massLve state, either in essentially the
pure state or supported upon or aarried by an inert or
,: ; catalytically ~activ~ supporting or carr.ier material, such
as pumica, kieselguhr, diatomaceous earth, clay, alumina
,
charcoal, carbon, or the like, and the reaction mixture
contacted therewith as by flowing the mixture over or
through a b~d of the catalyst or according to other methods
that are known in the art.
In the process of this invention rhenium or a
rhenium compound may optionally be used as a component of
the base metal hydrogenation catalyst for the purpose of
further extending the life of said catalyst. The rhenium
modified base hydrogenation catalysts of this invention may
be prepared by adding a solution of Re2O7 in water to~ e.g.,
nickel on alumina. The nickel on alumina absorbs the
rhenium and the xesulting catalyst is placed in a reactor
and treated with H2 at a temperature and pressure and or a
time that will reduce and insolubilize the Re2O7, e.g., at
1 atmosphere and 180C for 2 hours.
The hydrogenation and hydrolysis o this invention
is carried out at an elevated temperature under supera~mo-
spheric hydrogen pressure and in the presence of an aqueous
m2dium as well as in the presence of an acid hydrolysis
catalyst and the base metal h~drogenation catalyst.
Generally, the amount of water present is that amount that
is sufficient for the hydrolysis/hydrogenation step; that
is, a molar ratio of water to acetal of 1:1 to 100:1,
preferably 1:1 to 10:1. The hydrogen pressure is generally
from 500 to 10,000 psi~, preferably 1,000 to 5,000 p5.ig.
The temperature is generally 125 to 200C, preferably 125
to 175C.
The hydrolysis portion of the process of the
; present invention requires an acid catalyst. In view of
~ 30 the requirement that water ~e presen~ for the hydrolysis,
g3~i~
the acid is generally present as an aqueous acid. The
aqueous acid for the hydrolysis reaction may be selected
from a wide variety of acid-reacting materials and can be
used for imparting the required acidi~y to said aqueous
reaction medium. Acids and acid-reacting salts have both
been successfully used. Mineral acids such as sulfuric,
phosphoric and the like acids or such acid-acting salts
as sodium ~isulate, monosodium orthophosphate, aluminum
sulfate an~ the like may be used in the process of the
present invention. Water-soluble organic caxboxylic acids
are also acidifying agents for use in the process of this
invention. Particularly useful are the lower atty acids
o 1 to 4 carbon atoms, especially acetic, propionic,
isobutyric and normal butyric acids but polycarboxyli~
acids such as succinic, malonic, and adipic acids are
suitable. These organic acids are useful in amounts of
about 5 to lOQ~ by weight of the water used in the reaction.
However, a normality of ~rom about 0.005 to about 1 is
preferred. Insoluble acid ion exchange resins may also
be used in the process of the present invention.
In the preparation of the cyalic acetals
of the aforesaid general formula there is normally suf~i-
cient acid present wi~h the cyclic acetal to not require
the addition of acid beyond that present thereby. Thus
normally in order to maintain the pH within the in~ention,
it is necessary to add caustic~ Any caustic solution may
be usedO ~owever, because of availability and convenience
sodium hydroxide and potassium hydroxide are preferred.
The pH of the reaction mixture for the simulta~
neous hydrolysis/hydrog nation of this invention may be
10 --
. .. . . : . . . . . . :
maintained above 4.0 by merely the addition of caustic in
view of the presence of acids with the cyclic aldehydes of
this invention. At pH values below 4.0 the base metal
hydrogenation catalyst life is surprisingly short as
compared to values at 4~0 and above. Generally the upper
pH limit in the process of the present invention for main-
taining improved catalyst life is not critical. At pH
values up to 6.9 an acceptable hydrogenation rate may be
obtained. The upper limit on pH should be chosen to achieve
a hydrolysis rate such that the reaction is completed in an
acceptable len~th of time. Thus, while the pH ranye may
be generally from 4.0 to 6.9, the preferred pH range is 4.0
to 5.5. Most preferably the pH is 4.0 to 4.5~
In the process of the present invention the yiald
of 2-methyl-1,3-propanediol (MPD~ was found to be extremely
sensitive to pH. Th~ yield o MPD as a byproduct can be
substantially improved or maximized without a loss in yield
of 1,4-butanediol by controlling the pH in the pro ess of
~ ~ .
the present invention in the preerred range of 4.0 to 5.5,
most preferably 4.0 to 4.5.
A mixture within the scope o this invention,
2(2'-propanal)-4-methyl-1,3-dioxane and 2(3'-propanall-4-
methyl-1,3-dioxane, is simultaneously hydrogenated and
hydrolyzed in the presence of a nickel catalyst promoted
with rhenium and aqueous sulfuric acid to yield 1,4-butanediol
and 2-methyl 1,3-propanediol. The contxol of the pH of the
reaction mixture at from 4uO to 5.5 greatly extends the life
o the catalyst over that where he p~ of the reaction mix-
ture is below 4.0 and also, without a yield loss of 1,4-
butanediol, produces increased yields of 2 methyl-1,3-
propanediol.
- 11 - -
:-
.. . . .............. . . .
. . . . . . . .
Another mixture within the scope of this inven-
tion, 2(2'-propanol)-4-methyl-1~3-dioxane and 2(3'-propanol)-
4-methyl-],3-dioxane, is likewise simultaneously hydro-
genated and hydrolyzed without a yield loss of 1,4-butane-
diol, produces increased yields of 2-methyl-1,3-propanediol.
It i5 also within the scope of this invention to u~e mix-
tures of 2(2'-propanal)-5-methyl-1,3-dioxane and 2(3'-
propanal)-S-methyl-1,3-dioxane and mixtures of 2(2'-
propanol)-5-methyl-1,3 dioxane and 2(3'-propanol 5-methyl- ;
1,3-dioxane.
The 1,4-butanediol prepared by the process of
this invention may b~ separated from the byproduct diol(s)
present therewith if desired. Where the diol is 2-methyl-
1,3-propanediol, the separation with 1,4-butanediol is
relatively simple due to the difference in boi~ing points.
In any event, the byproduct diol(s~ is separated from the
1,4-~utanediol by conve~tional means.
~.
As can be seen from the aforesaid cyclic acetal
general ~o~nula the process o the present invention in-
cludes within its scope the step of prehydrogenating kh~
acetal aldehydes in the presence oE a hydrogenation aata-
lyst prior to the simultaneous hydrolysis and hydrogenation
in Xhe presence of the base metal hydrogenation catalyst
and aqueous acid according to the process of the present
invention. This prehydrogenation is conducted at normal
hydrogenation conditions,except for temperature, in the
presence of a base metal hydrogenation catalyst. The pre~
hydrogenation converts the -CHO gxoup to -CH20H before any
hyarolysis of the starting compound.
The prehydrogenation, if desired, may be carried
out in an aqueous medium in which case the water acts as a
12
:
hea-t sink and a viscosity adjustor although the reaction can
also be carried out neat; that is, without the use of water.
If an aqueous medium is used, it is convenient to have enough
water present ~or the hydrolysis-hydrogenation stepthat follows.
The prehydrogenation is conducted at a temperature
of from ~0 to 125C. Temperatures above 125C will tend to
promote simultaneous hydrolysis and hydrogenation.
The pressure for the prehydrogenation is generally
from 500 to 10,000 psig, preferably 1,000 to 5,000 psig.
The prehydrogenation results in the preparation of
compounds with t'he aforesaid general formula where X is CH2OH.
Thus, the process of the present invention comprlses the simul~
taneous catalytic hydrogenation and hydrolysis at a p~I o~ 4 to
5.5 of compounds of the general formula gi~en above where X is
-CHO as well as where X is -C~I2OH.
The process of the present invention is further
described by re~erence to specific cyclic acetals. It will be
understood, however, that the process of the invention is
equally applicable to the cyclic acetals of the general formula
given a~ove.
I'he cyclic acetals of the present invention may be
prepared by the reaction of an alcohol and/or diol having at
least four carbon atoms and a maximum of three carbon atoms
separating the diol hydro~y groups with at least a stoichio-
metrical]y equivalent quantity of an aldehyde and/or dialdehyde
after which hydroformylation produces the cyclic acetals. U.S.
, Patent ~ 024 159 which issued 1977 May 17 discloses the pre- ':
- paration of the cycllc acetals. U.S. ~atents 3,963,754 and
3,963,755 disclose the preparation oE'2(3'-propanal)-5-methyl-l,
3-dio~ane and 2~2'-propanal)-5--methyl-1,3-dioxane. Other '
: , '
- 13 -
'
1~ .
!, . .. . ..
cyclic acetals may be prepared according to the disclosure
in the aforesaid patents. The starting compounds of this
invention of the aforesaid general formula where X is CH2OH
are prepared by the hydrogenation of the cyclic acetals alde-
hydes under hydrogenation conditions described herein in the
presence of the base metal hydrogenation catalysts of this
invention also indicated herein as ~rehydrogenation.
The process of the invention is useful in the pre-
paration of 1,4-butanediol which can be converted to tetra-
hydrofuran both of which are useful as solvents.
The examples were all conducted with the indicated
4-methyl aldehydes (from the readily available 1,3-butanediol)
rather than the 5-methyl aldehydes ~from the less readily
availahle MPD). Tests, however, indicate no major differences
between the performance of the 4-methyl aldehydes and the
5-methyl aldehydes.
The following examples further illustrate the inven-
tion. All percentages are by weight unless otherwise indicated
EXAMPLE 1
A 100 g sample of nickel catalyst was charged to a
1-1/2" diameter high pressure tubular reactor. rro this was
fed 85~ 2(3'-propanal)-4-methyl-1,3-dioxane and 153
2(2'-propanal)-4-methyl-1,3-dioxane and H2O at a 2:1 weight
ratio of acetal to water at 270 ml/ hr together with a 5:1
weight ratio oE recycle of reactor product to acetal and
water feed. The hydrogenation catalyst bed was maintained
at 155C and 2,000 psig H2 pressure.
The catalyst was 50~ Ni on kieselguhr and no
- 14 -
~i .
-
5~S~
attempt was made to control pH. The initial pH of the
product was 5.0, but after one day th~ pH fell below 4.0
at which time the catalyst activity fell to le~s than half
of its original value.
EXA~LE 2 -
The procedure of Example 1 was ollowed except
that the pH of the reactor mixture was maintained at 5.0
to 5.5 by addi~ion of a small amount of NaOH via the H2O
feed (0.006N NaOH) throughout the reaction. The catalyst
survived for eight days before it suddenly lost most of
its activity. The yield of 1/4~butanediol remained con-
stant for the first eight days at the run at 85%. However,
at that point the yield declined rapidly down to 54~ indi-
cating a loss in catalyst activity.
EXAMPLE 3
The procedure of Example 1 was ollowed except
that the catalyst was 1/8 inch diameter pellets of 50% Ni
on alumina and no control was exerted over pH. The initial
pH of the reactor mixture was 5Ø Over the first four
days the pH gradually drifted down to 4.0, but the activity
; remained at its original high value. On the fifth day, the
pH fell below 4.0, and the catalyst lost more than half of
its oriyinal activity as determined by the loss o yield of
1,4-butanediol and MPD to about 50% of the yield of the
first four days.
EXAMPLE 4
~ The procedure of Example 1 was followed except ~ ;
that the cataly~t wa~ prepared by adding a solution of 5~0 g
Re O in 25 ml ~2 to a fresh 100 g sample of the same Ni
2 7
on alumina catalyst used in Example 3. The solution was
:'
~: :
- 15 ~ ~
completely absorbed by the catalyst. The catalyst was placed
in ~he reactor and treated with H2 at 1 atm at 180C for
2 hours to reduce and insolubilize the Re2O7~ Duriny this
run the pH was controlled at 4.0 to 5.5 by addition of NaOH
to the water feed (0.0012N NaOH). This run was carried out
for 19 days, and there was no siynificant loss of catalyst
activity. The effect of p~I on yield of 1,4-butanediol,
2-methyl-1,3-propanediol (MPD), branched and linear hydroxy
acetal is summarized in the table that follows:
'. ~ '
- 16 -
.~o oo o o o~ o
0.~ c~
E~,,,
a) a~ oo ~ a~
'
s~
: ~ ~ 0
~, o o u~
co ~ ~
~ rl O
~
E~
: ~ l CO ~ Ln Ln C~ Ln In tn N ~ 'I '
~ 7 m ~ ~ OD C~
O ~D Ln f~
n Ln Ln d~
~ ~ - 17 -
- :, , ~ , .. .
:: - . . ' .
Thus, it can be se~n that the yiel.d of MPD de
creases with i.ncreasing pH. While the unreacted BHA yield
loss can be overcome with further hydrolysis and hydro~
genation to MPD with extended reaction ti~es, this would be
disadvantageous.
EXAMPLE 5
-
The procedure of Example 1 was followed, except
the catalyst was 200 g of Raney nickel ~5% aluminum re-
moved). During the run the pH was mainta.ined at 4.5 to 5.0
by addition of NaOH with the water feed. The run was
carried out for 10 days during which ~ime the yield of
1,4-butanediol was between 85 and 87%, the MPD yield was
between 70 to 85%, and the catalyst showed no sign of loss
of activity.
EXAMPLE 6
The procedure of Example 4 was repeated except
that the particle size of the catalyst of Example 3 was
decreased to 1/16 inch diameter particles. The run was
carried out for 55 days. The acti.vity of the catalyst
began to decrease after about 35 days as evidenced by a
decrease in BAD and MPD yield. The pH was controlled at
4.0 to 5Ø The yield of BAD for the first 45 days was
greater than 95% while the ~PD was 85 to 100% for the first
35 days.
Whlle the invention has been described in consid-
erable detaLl in the ~oregoing, it is to be understood that
such detail is solely for the purpose of illustration and
that variations can be made by those skilled in the art
withou~ departing ~rom the spirit and scope of the invention
except as sèt forth in the claims.
. . .
' .
- 18 -
.
